MERCURIC IODIDE DETECTOR SYSTEMS FOR IDENTIFYING SUBSTANCES BY X-RAY-ENERGY DISPERSIVE DIFFRACTION

The use of mercuric iodide arrays for energy-dispersive x-ray diffract ion (EDXRD) spectroscopy is now being investigated by us for inspectio n of specific crystalline powders in substances ranging from explosive s to illicit drugs. Mercuric iodide has been identified as the leading candidate for replacing the Ge detectors previously employed in the d evelopment of this technique because HgI2 detectors: operate at or nea r room temperature; without the bulky apparatus associated with cryoge nic cooling; and offer excellent spectroscopy performance with extreme ly high efficiency. Furthermore, they provide the practicality of cons tructing optimal array geometries necessary for these measurements. Pr oof of principle experiments have been performed using a single-HgI2 d etector spectrometer, An energy resolution of 655 eV (FWHM) has been o btained for 60 keV gamma line from an (241) Am source. The EDXRD signa tures of various crystalline powdered compounds have been measured and the spectra obtained show the excellent potential of mercuric iodide for this application.